Why: The CPU (Central Processing Unit) is often referred to as the "brain" of the computer because it performs most of the processing tasks, executes instructions from programs, performs calculations, and controls other components. It consists of the arithmetic logic unit (ALU) for calculations and the control unit (CU) for coordinating operations. Among the options, B) CPU is correct.

Why: The motherboard is the main circuit board that serves as the central hub connecting all major components like CPU, RAM, storage devices, and expansion cards via slots, buses, and ports. It provides pathways for data, power, and signals between components. Among the options, B) Motherboard is correct.

Why: RAM (Random Access Memory) is the main memory of the computer, used for temporary storage of data and programs currently in use. It is volatile, meaning data is lost when power is off, and allows fast read/write access. Among the options, D) RAM is correct.

Why: The system bus is a communication pathway that connects the CPU to other hardware components like memory and I/O devices, transferring data, addresses, and control signals. It includes data bus, address bus, and control bus. Among the options, A) System Bus is correct.

Why: A keyboard is an input device that allows users to enter data and commands into the computer by typing. It sends electrical signals corresponding to keystrokes to the CPU via the motherboard. Among the options, C) Keyboard is correct.